diff --git a/sys/kern/kern_xxx.c b/sys/kern/kern_xxx.c
index ea3c0b402b59..6b3d5f005d3f 100644
--- a/sys/kern/kern_xxx.c
+++ b/sys/kern/kern_xxx.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: kern_xxx.c,v 1.33 1996/08/09 10:30:23 mrg Exp $	*/
+/*	$NetBSD: kern_xxx.c,v 1.34 1996/08/10 00:23:17 mrg Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -57,13 +57,22 @@ sys_reboot(p, v, retval)
 		syscallarg(char *) bootstr;
 	} */ *uap = v;
 	int error;
+	char *bootstr;
 
 	if ((error = suser(p->p_ucred, &p->p_acflag)) != 0)
 		return (error);
+
+	/*
+	 * Only use the boot string if RB_STRING is set.
+	 */
+	if (SCARG(uap, opt) & RB_STRING)
+		bootstr = SCARG(uap, bootstr);
+	else
+		bootstr = NULL;
 	/*
 	 * Not all ports use the bootstr currently.
 	 */
-	boot(SCARG(uap, opt), SCARG(uap, bootstr));
+	boot(SCARG(uap, opt), bootstr);
 	return (0);
 }
 
diff --git a/sys/sys/reboot.h b/sys/sys/reboot.h
index d927ec50b876..15d907e44fe8 100644
--- a/sys/sys/reboot.h
+++ b/sys/sys/reboot.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: reboot.h,v 1.10 1996/08/09 10:30:23 mrg Exp $	*/
+/*	$NetBSD: reboot.h,v 1.11 1996/08/10 00:23:14 mrg Exp $	*/
 
 /*
  * Copyright (c) 1982, 1986, 1988, 1993, 1994
@@ -51,6 +51,7 @@
 #define	RB_RDONLY	0x080	/* mount root fs read-only */
 #define	RB_DUMP		0x100	/* dump kernel memory before reboot */
 #define	RB_MINIROOT	0x200	/* mini-root present in memory at boot time */
+#define RB_STRING	0x400	/* use provided bootstr */
 
 /*
  * Constants for converting boot-style device number to type,